Sequestrant compositions

ABSTRACT

DISCLOSED ARE SEQUESTRANT COMPOSITIONS COMPRISING A MIXTURE OF (1) A COMPOUND SELECTED FROM THE GROUP CONSISTING OF CITRIC ACID, TARTARIC ACID, POLYHYDROXY MONOCARBOXYLIC ACIDS CONTAINING FROM 6 TO 8 CARBON ATOMS, AND THE WATER SOLUBLE SALTS OF SAID ACIDS AND (2) A COMPOUND SELECTED FROM THE GROUP CONSISTING OF POLYHYDROXY DICARBOXYLIC ACIDS CONTAINING FROM 5 TO 8 CARBON ATOMS AND POLYHYDROXY MONOCARBOXYLIC KETOACIDS CONTAINING FROM 6 TO 8 CARBON ATOMS AND THE WATER-SOLUBLE SALTS OF SAID ACIDS.

United States Patent 3,696,044 SEQUESTRANT COMPOSITIONS Thomas F. Rutledge, Wilmington, Del., assignor to Atlas Chemical Industries, Inc., Wilmington, Del. No Drawing. Filed July 2, 1970, Ser. No. 52,088 Int. Cl. C02b 5/06; C23g 1/02 U.S. Cl. 252-180 Claims ABSTRACT OF THE DISCLOSURE Disclosed are sequestrant compositions comprising a mixture of (l) a compound selected from the group consisting of citric acid, tartaric acid, polyhydroxy monocarboxylic acids containing from 6 to 8 carbon atoms, and the water soluble salts of said acids and (2) a compound selected from the group consisting of polyhydroxy dicarboxylic acids containing from 5 to 8 carbon atoms and polyhydroxy monocarboxylic ketoacids containing from 6 to 8 carbon atoms and the water-soluble salts of said acids.

This invention relates to new compositions of matter. More particularly, this invention relates to novel sequestrant compositions comprising a mixture of sequestering agents.

The commercial cleansing of bottles by industries requiring reconditioning of glassware is reliant upon the employment of a strong caustic solution followed by a rinse. Such washing methods are generally satisfactory provided that some provision is made to prevent the precipitation of salts of calcium, magnesium, aluminum, iron, and other insoluble metallic components. In the absence of such provisions, the insoluble metallic salts are precipitated as a scale, both on the glassware and on the Washing machinery. Thus, sequestering agents are normally employed in combination with the caustic solutions to prevent the precipitation of insoluble metallic salts.

Polyhydroxy acids, such as gluconic acid, are widely used to sequester calcium ions in basic solutions. Detergent formulations used for bottle washing frequently contain gluconic acid (sodium gluconate in the basic medium). Gluconic acid is a good sequestrant for calcium ions, but it is not nearly as good as alpha-ketoglucom'c acid and the polyhydroxy polycarboxylic acids such as saccharic acid and mucic acid. These more efficient acids,

.however, are considerably more expensive than gluconic acid.

It has now been discovered in accordance with the present invention that certain mixtures of sequestering agents exhibit unexpectedly improved or synergistic behavior in sequestering calcium ion in basic solutions. It has been discovered that mixtures containing a minor amount:- of certain powerful sequestrant and a major amount of certain relatively poor sequestrant are actually as effective as the powerful sequestrant agent alone. Thus, excellent sequestering agents can now be made by using a mixture of at least one relatively weak sequestrant and a minor amount of at least one more powerful sequestrant. For example, a mixture of gluconic acid and a minor amount of saccharic acid is nearly as effective as a pure saccharic acid alone in sequestering calcium ions. This is the first known observation of synergism in mixtures of organic sequestering agents.

The novel compositions of the present invention comprise a mixture of (1) a compound selected from the group consisting of citric acid, tartaric acid, polyhydroxy monocarboxylic acids containing from 6 to 8 carbon atoms, and the water soluble salts of said acids and 3,696,044 Patented Oct. 3, 1972 ice (2) a compound selected from the group consisting of polyhydroxy dicarboxylic acids containing from 5 to 8 carbon atoms, polyhdroxy monocarboxylic ketoacids containing from 6 to 8 carbon atoms, and the water soluble salts of said acids.

Illustrative examples of polyhydroxy monocarboxylic acids which may be used in the compositions of this invention include gluconic acid, gulonic acid, glucoheptanoic acid, and glucooctanoic acid. A preferred class of polyhydroxy monocarboxylic acids and water-soluble salts thereof which may be used as a component of the sequestering compositions of this invention includes the compounds characterized by the following generalized formula COO-X (CHOHL;

CHQOH C O O Q (JIHOHLD OOD wherein m is 3 or 4 and wherein Q and D are independently hydrogen or cation.

Illustrative examples of polyhydroxy monocarboxylic ketoacids,includeZ-ketogulonic acid, 2-ketogluconic acid, S-ketogluconic acid, Z-ketoglucoheptanoic acid, 3-ketogluconic acid, 4-ketogluconic acid, 3-ketogulonic acid, and 4-ketogulonic acid. A preferred keto acid is 2-ketogluconic acid.

In view of the fact that the sequestering compositions of this invention are normally employed in combination with strong caustic solutions, it is immaterial whether the sequestering agents are employed in the free acid form or in the salt form. Thus, compounds (1) and (2) described above may be employed in free acid form or as a water soluble salt. Illustrative examples of such salts include the alkali metal and ammonium salts. A preferred class of salts includes the sodium and potassium salts.

The amounts of compounds (1) and (2) described above which may be employed in the sequestering compositions of this invention may vary a wide range and will depend somewhat on the sepcific combination of sequestering agent used, on the cost of the sequestering agent, and on the particular system in which the the sequestering composition is employed. In general, the weight ratio of compound 1) to compound (2) is not more than about 100 and at least about 0.05 and preferably at least about 1. A particularly preferred weight ratio of compound (1) to compound (2) is from about 2 to about 10.

A preferred composition of this invention comprises a mixture of about parts by weight of gluconic acid or water-soluble salt thereof and about 25 parts by weight of saccharic acid or water-soluble salt thereof.

In order that those skilled in the art may better understand how the present invention may be practiced, the following examples are given. These examples are set forth solely for the purpose of illustration and any specific enumeration of details obtained therein should not be interpreted as expressing limitations of this invention. All parts and percentages are by weight unless otherwise stated.

In the following examples, the calcium sequestering ability of the various compositions is determined by the titration of 0.2 gram of the active material with one percent calcium acetate solution and three percent caustic solution in accordance with a modified version of a test described by Mehltretter et al., Industrial Engineering Chemistry, 45,2782 (1953). A two percent stock solution of the sequestring agent is prepared, and ten ml. of this stock solution are diluted with ml. of a six percent sodium hydroxide solution and two ml. of two percent sodium oxalate solution. The diluted solution is mechanically stirred, and a standard one percent calcium acetate solution is added from a syringe attached to a constant speed syringe pump until a slight haze is observed in the solution. The amount of calcium ion added is a measure of the sequestering power of the sequestering agent under test. Sodium gluconate, a standard of the industry, is arbitrarily assigned a calcium ion sequestering index of 1.00. The calcium ion sequestering power of the other sequestrants are calculated based on sodium gluconate. Thus, disodium saccharate has an index of 2.72 which indicates that disodium saccharate is 2.72 times as effective as sodium gluconate. The calculated calcium ion sequestering power is determined by adding the theoretical calcium ion sequestering power of each component of the sequestering composition. For example, the calculated calcium ion sequestering power of a blend of 0.1 part of saccharic acid and 0.1 part of gluconic acid is obtained by adding one-half of the sequestering power of 0.2 part of saccharic acid and one-half of the sequestering power of 0.2 part of gluconic acid (2.72/2+l.00/2=l.86). The synergism index is obtained by subtracting the calculated calcium ion sequestering power from the observed calcium ion sequestering power (2.47-1.86-=+0.6l). The results obtained are set forth in the following tables.

TABLE I.CALCIUM ION SEQUESTERINDC?I The sequestering compositions of this invention may be used in any of the numerous ways known in the art for using sequestering agents. For example, the sequestering compositions may be used alone or in combination with wetting agents, surfactants, detergent builders, detergent compositions, and other ingredients which are used in the art in combination with sequestering agents.

Although this invention has been described with reference to sequestering agents and to specific mixtures of sequestering agents, it will be appreciated that numerous other sequestrants and mixtures of sequestrants may be substituted for those described, all within the spirit and scope of this invention.

What is claimed is:

1. A composition comprising a mixture of (1) a compound selected from the group consisting of citric acid, tartaric acid, polyhydroxy monocarboxylic acids containing from 6 to 8 carbon atoms, and the water soluble salts of said acids and (2) a compound selected from the group consisting of polyhydroxy dicarboxylic acids containing from 5 to 8 carbon atoms, polyhydroxy monocarboxylic ketoacids containing from 6 to 8 carbon atoms, and the water soluble salts of said acids.

2. A composition of claim 1 wherein the polyhydroxy monocarboxylic acid containing from 6 to 8 carbon atoms 2D has the formula COOX wherein n is an integer from 4 to 6 and wherein X is hydrogen or a cation.

3. A composition of claim 2 wherein the weight ratio r of compound 1) to compound (2) is at least one. 4. A composition of claim 3 wherein compound (1) has the formula HOH 40 HzOH POWER OF SODIUM SACCHARATE, SODIUM GLUCONATE, AND

IXTURES THEREOF Percent sodium saccharate Percent sodium gluoonate 0 Calcium ion sequestering power (gluconate= 1. 47 2. 47 2. 72 2. 75 1. 83 1. 75 1.19 1. 00 Calculated calcium ion sequestering pow 2. 03 1. 86 1. 52 1. 43 1. 26 1. 17 1. 09 Syncrgism index +0. 44 +0. 61 +1. 21 +1. 32 +0. 57 +0. 58 +0. 10

TABLE II.-CALCIUM ION SEQUESTERING POWER OF SODIUM 2-KETO GULONATE, SODIUM GLUCONATE, AND MIXTURES THEREOF l. 42 1. 35 1. 27 Synergism index +0. 30 +0. 51 +0. 68

TABLE IIL-CALCIUM ION SEQUESTERING POWER OF SODIUM MUCATE, POTASSIUM SODIUM TARTRATE, AND MIXTURES THEREOF Percent sodium mucate Percent KNa tartrate 0 60 80 85 90 100 Calcium ion sequestering power (gluconete=l.00) 2. 82 2. 20 1. 88 1. 88 1. 40 1. 25

Calculated calcium ion sequestering power 1.88 1.56 1.48 Synergismindex +0.32 +0.32 +0.40

wherein n is an integer having a value of from 4 to 6 and X is hydrogen or cation and wherein compound (2) has the formula wherein m is 3 or 4 and Q and D are independently hydrogen or cation.

5. A composition of claim 2 wherein the ratio of compound (1) to compound (2) is from 2 to 10.

6. A composition of claim 5 wherein compound (1) is gluconic acid or a water soluble salt of glyconic acid.

7. A composition of claim 6' wherein compound (2) is saccharic acid or a water soluble salt of saccharic aid.

8. A composition of claim 6 wherein compound (2) is Z-ketogluconic acid or a water-soluble salt of 2-ketogluconic acid.

9. A composition of claim 8 wherein the ratio of compound (1) to compound (2) is from 2 to 10.

5 6 10. A- composition of claim 2 wherein the polyhydroxy 3,095,862 7/ 1963 Berner 252-180 X dicarboxylic acid containing from 5 to 8 carbon atoms 3,150,081 9/1964 Haslam 134-41 X has the formula 3,510,351 5/1970 Dillen 1343 X 323; OTHER REFERENCES mm m Mehltretter et a1.: Sequestration by Sugar Acids, -Industrial and Engineering Chemistry, v01. 45, No. 12, pp. wherein m is 3 or 4 and wherein Q and D are independent- 2782-2784, December 1953. 1y hydrogen or a cation.

10 ROBERT F. BURNETT, Primary Examiner Refe'ences Cited M. E. MCCAMISH, Assistant Examiner UNITED STATES PATENTS 3,328,304 6/1967 Globus 252180 X 3,012,502 1/1963 Alfano 134-3 21-21; 134-3, 41; 210-58; 252-82 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTTON Patent No. 3,696,044 Dated c r 1972 lnventor( F a It is certified .that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 56, after "vary" and before "a" insert the word over Column 2, line 57, "sepcific" is misspelled and should read specific Column 3, Table I, "Percent'sodium saccharate" should appear'above "Percent sodium gluconate" not above the numbers. Column 3, Table II, in the title "2-KETOGULONATE, SODIUM GLUCONATE," should be underscored.

Column 3, Table II, "Percent 2-ketogulonate" should appear above "Percent glucona te" not above the numbers.

Column 3, Table III, in the title "SODIUM MUC ATE,

POTASSIUM SODIUM TARTRATEI should be underscored.

Column 3, Table III, "Percent sodium mucate" should appear above "PercentKNa tartrate" not above the numbers.

Column 4, Claim 4, line 1, after "claim" the "3" should read 2 Column4, Claim 6, line 2, after "of" theword "glyconic" is misspelled and should read gluconic Signed and sealed this 22nd day of May l973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. I I ROBERT GOTTSCHALK Attesting Officer I Commissioner of Patents I FORM Po-1o5o (10-69) USCOMM-DC 50376-1 69 ".5. GOVERNMENT PRINTING OFFICE 1965 0-365-334, 

